Determination Of Picogram Amounts Research Articles

Determination of picogram quantities of chlortoluron in soil samples by luminol–chitosan chemiluminescence system

Based on the enhancing effect of chitosan (CS) on luminol-dissolved oxygen chemiluminescence (CL) reaction, a flow injection (FI) luminol-CS CL system was established. It was found that the increase of CL intensity was proportional to the concentrations of CS ranging from 0.7 to 10.0 μmol l(-1). In the presence of chlortoluron (CTU), the CL intensity of luminol-CS system could be obviously inhibited and the decrements of CL intensity were linearly proportional to the logarithm of CTU concentrations ranging from 0.01 to 70.0 ng ml(-1), giving the limit of detection 3.0 pg ml(-1) (3σ). At a flow rate of 2.0 ml min(-1), the whole process including sampling and washing could be accomplished within 36 s, offering a sample throughput of 100 h(-1). The proposed FI-CL method was successfully applied to the determination of CTU in soil samples with recoveries ranging from 95.0 % to 105.3 % and the relative standard deviations (RSDs) of less than 4.0 %.

Nonspecific Particle-Based Method with Two-Photon Excitation Detection for Sensitive Protein Quantification and Cell Counting

A novel easy-to-use homogeneous method utilizing two-photon excitation (TPX) for quantification of proteins or counting of eukaryotic cells in solution has been developed. This highly sensitive technique is based on the adsorption competition between the sample and fluorescently labeled protein to micrometer-sized carboxylate modified polystyrene particles and detection of two-photon excited fluorescence. The adsorption of the labeled protein to the particles was detected as a distinct fluorescence on individual microparticles. Analyte protein or eukaryotic cells interacted with particle surface and reduced the adsorption of labeled protein to the particles resulting in a decrease of the fluorescence. The optimizations of assay conditions were performed separately for protein quantification and cell counting, and the principle of the method was confirmed with the fluorescence microscopy imaging. The protein quantification assay allowed the determination of picogram quantities (1.2 μg/L) of protein, and the cell counting assay allowed three cells in the sample with an average variation of approximately 10% in the signal. The protein assay sensitivity was more than 500-fold improved from the common most sensitive commercial methods. Moreover, the dynamic range of the assay was broad, approximately 4 orders of magnitude. The cell assay has sensitivity comparable to the most sensitive commercial method. The developed method tolerates interfering agents such as neutral detergents found in cell lysate samples even at high concentrations. The method is experimentally fairly simple and allows the expansion for the use of the TPX technology.

Ultrasensitive Protein Concentration Measurement Based on Particle Adsorption and Fluorescence Quenching

A new easy-to-use method for quantification of proteins in solution has been developed. It is based on adsorption competition of the sample protein and fluorescently labeled bovine serum albumin (BSA) onto gold particles. The protein concentration is determined by observing the magnitude of fluorescence altered by quenching the fluorescence on the gold particles in a homogeneous assay format. Under optimal low pH conditions, the assay allowed the determination of picogram quantities (7.0 microg/L) of proteins with an average variation of 4.5% in a 10 min assay. The assay sensitivity was more than 10-fold improved from those of the commonly used most sensitive commercial methods. In addition, the particle sensor provides a simple and rapid assay format without requirements for hazardous test compounds and elevated temperature. Eleven different proteins were tested with the constructed sensor exhibiting a protein-to-protein variability less than 15% allowing protein concentration measurements without the need for recalibration of different proteins.

Radioimniunoassay of Aescine, a Mixture of Triterpene Glycosides

A radioimmunoassay (RIA) has been developed for the determination of picogram amounts of aescine, an anti-inflammatory and anti-oedematous glycoside mixture from unpurified extracts of Aesculus hippocastanum. Practically no interference is observed for various potentially crossreacting compounds. This RIA covers the range 100 pg-50 ng, within which acceptable accuracy and precision are obtained.

Successive Determination of Picogram Amounts of Phosphorus and Arsenic in Pure Water by Indirect Flameless Atomic Absorption (Mo) Spectroscopy

Abstract The method involves the conversion of the P and As into the yellow 12-molybdo-phosphate or - arsenate complex, respectively, extraction into butyl acetate (in the case of As - with the preliminary addition of ethanol), the decomposition of the heteropoly-compounds with aqueous NH3 and the back extraction of the liberated Mo into aqueous solution, for flameless AA determination. 10 pg P and 25 pg As in 0.4 ml samples of ultrapure water were determined with percentage errors below ±30%.